Image sensors are semiconductor devices which convert an optical image into an electrical signal. Image sensors may be divided into change coupled device (CCD) image sensors and complementary metal oxide silicon (CMOS) image sensors (CIS).
A CMOS image sensor includes a photo diode and a MOS transistor in each of unit pixels, and thus, sequentially detects electrical signals of the respective unit pixels in a switching mode, thereby displaying an image. A CMOS image sensor is divided into photo diode regions, receive a light signal and converts the light signal into an electric signal, and transistor regions, which process the electric signal. In a CMOS image sensor, micro lenses for light concentration are formed on and/or over the upper end of the sensor. The micro lenses are made of an organic material, and are completed through processes, such as a photo etching process (PEP) and a reflow process.
However, the organic material has weak mechanical characteristics, and thus is sensitive to defects. Foreign substances are generated during a subsequent process after the formation of the micro lenses and are attached to the micro lenses, thereby causing a malfunction of the CMOS image sensor. Further, CMOS image sensor may generate image interference due to crosstalk between pixels.